Multi-site land mobile radio systems typically utilize leased communication lines to interconnect radio repeater infrastructure devices (e.g., fixed base stations) with a central call control server. The recurring costs of the leased communication lines, as well as the capital investment required to deploy multiple radio repeater infrastructure entities and a specialized call control server can result in relatively high system costs. Multi-site land mobile radio systems are primarily utilized to provide emergency communications to police officers, fire fighters and other emergency responders.
Professional and commercial entities, such as retail store chains, school systems, utilities companies, transportation companies and construction companies, can also benefit from the use of multi-site land mobile radio systems but, due to the recurring costs and the required capital investment, such entities generally do not deploy such systems. Companies who operate over large geographic areas or in different regions may require hundreds or even thousands of fixed radio repeater base stations to implement a suitable multi-site wide area land mobile radio system. Moreover, such a system would require multiple central call servers, which themselves would need to be connected over separate leased lines, thus creating significant additional operational expenses.
One alternative for enabling peer-to-peer communications between users of such entities are two-way radio dispatch systems designed to operate over a wide area network (WAN). The two-way radio dispatch system includes multiple sites distributed over a wide area. At each physical site a minimal complexity base station is provided. Each base station can locate and establish connections to other peer base stations deployed at other physical sites directly over the Internet (or other WAN). As such, the peer base stations can communicate with each other over an Internet Protocol (IP) network without communicating through a centralized call control center, such as a Mobile Switching Center (MSC), or public telephone network, etc. This greatly reduces the costs for the entities that purchase the base stations devices to set up a two-way radio dispatch system. Once the peer base stations have established a connection with one another other over the Internet, the infrastructure for setting up a two-way radio dispatch system is deployed, and wireless communication devices located at one particular physical site can then communicate (via the base station) with other wireless communication devices located at the other physical sites. Industries including transportation, education, construction, manufacturing, energy and utilities, private security, government, hospitality, retail, and many others are finding that these two-way radio systems are relatively easy and inexpensive to deploy, and that they can improve efficiency, worker productivity and responsiveness by allowing mobile teams to share business and customer information instantly.
In many cases, such two-way radio systems support group communication or “group call” functionality for allowing simultaneous communications to a group of mobile wireless communications devices (WCDs). However, problems can arise when the number of communication groups attempting to simultaneously communicate with a base station exceeds the maximum number of inbound radio frequency (RF) resources (IRFRs) available at the base station. For instance, base stations used in some two-way radio systems can only simultaneously support inbound communications of a small fixed number (e.g., two or four) of communication groups using different RF sub-channels or different time slots within of a particular RF sub-channel. Also base stations used in some two-way radio systems can only simultaneously support outbound communications of a small fixed number of communication groups using different RF sub-channels or different time slots within of a particular RF sub-channel. In such a system, if the number of simultaneous group communications exceeds the fixed number of outbound RF resources (ORFRs) at a site, then there will not be RF resources for at least one of the group communications and end-users might mistakenly believe that their group communications are sucessfully completed when there are not adequate RF resources to support them.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.